# [CRIT] [GHSA / CRITICAL] CVE-2026-55255: Langflow: IDOR Vulnerability in `/api/v1/responses` Endpoint Allows Authenticated Attackers to Access Another User's Flow

**Source:** GitHub Security Advisories
**Published:** 2026-06-19
**Article:** https://github.com/advisories/GHSA-qrpv-q767-xqq2

## Threat Profile

Langflow: IDOR Vulnerability in `/api/v1/responses` Endpoint Allows Authenticated Attackers to Access Another User's Flow

## Summary

Insecure Direct Object Reference (IDOR) vulnerability in `/api/v1/responses` endpoint allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request.

## Details

The vulnerability exists in the `get_flow_by_id_or_endpoint_name` helper function in [`src/backend/base/langflow/helpers/flow.py` (lines…

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2026-55255`

## MITRE ATT&CK Techniques

- **T1190** — Exploit Public-Facing Application
- **T1213** — Data from Information Repositories

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### Langflow IDOR endpoint access — POST to /api/v1/responses (CVE-2026-55255)

`UC_8_1` · phase: **exploit** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count from datamodel=Web.Web where Web.http_method=POST AND (Web.url="*/api/v1/responses*" OR Web.url="*/api/v2/workflow*" OR Web.url="*/api/v1/run*") by Web.src, Web.dest, Web.user, Web.url, Web.status, _time span=1m
| `drop_dm_object_name("Web")`
| sort - _time
```

### Langflow IDOR enumeration — single source fan-out to /api/v1/responses (CVE-2026-55255)

`UC_8_2` · phase: **recon** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count from datamodel=Web.Web where Web.http_method=POST AND Web.url="*/api/v1/responses*" by Web.src, Web.user, _time span=5m
| `drop_dm_object_name("Web")`
| where count > 20
| sort - count
```

### Asset exposure — Langflow instances vulnerable to CVE-2026-55255 (<1.9.1)

`UC_8_3` · phase: **recon** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count from datamodel=Vulnerabilities.Vulnerabilities where Vulnerabilities.cve="CVE-2026-55255" by Vulnerabilities.dest, Vulnerabilities.signature, Vulnerabilities.severity
| `drop_dm_object_name("Vulnerabilities")`
| sort - count
```

**Defender KQL:**
```kql
DeviceTvmSoftwareVulnerabilities
| where CveId == "CVE-2026-55255"
| join kind=leftouter (DeviceInfo | summarize arg_max(Timestamp, IsInternetFacing) by DeviceId) on DeviceId
| project DeviceName, DeviceId, SoftwareVendor, SoftwareName, SoftwareVersion, CveId, VulnerabilitySeverityLevel, RecommendedSecurityUpdate, IsInternetFacing
| order by IsInternetFacing desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2026-55255`


## Why this matters

Severity classified as **CRIT** based on: CVE present, 4 use case(s) fired, 2 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.